This invention is related to an apparatus for applying tape to joints between sections of pre-fabricated wall board.
Self-contained drywall taping apparatus are well known in the industry. These apparatus typically contain a long hollow tube which is filled with mastic utilizing a pump fed from a mastic supply. On the end of the hollow tube, a nozzle is attached. The nozzle serves to both feed tape and apply mastic to the tape and wall joint.
Several examples of drywall taping apparatus are taught by Ames in U.S. Pat. Nos. 4,086,121 and 2,815,142 and by Eccleston in U.S. Pat. No. 4,828,647. As best shown in U.S. Pat. No. 4,828,647, the Eccleston apparatus comprises a tubular body 14 which serves as a handle or grip and holds a quantity of mastic. The interior of the body 14 is provided with a piston and means for actuating the piston to extruded mastic. An outlet positioned adjacent a feeding path is provided for extruding the mastic onto the tape. Drive wheels 17 are mounted on a shaft and serve as the motive force for the apparatus as it is moved along the wall. A sprocket 27 rotates with the wheels 17 to operate a piston inside the main body 14 for extruding the mastic.
The nozzles of these taping apparatus are typically formed of metallic components which are precisely machined and fastened together with screws. The components are typically formed of stainless steel or aluminum and are precisely machined to receive the screws into threaded openings. The many components are best shown in FIG. 1. This prior art nozzle 1 consists of a filler tube inlet 2 which is screwed to a pair of side walls 3,4 with screws 5 in threaded openings 6. A stabilizer 7 secures the taping guide track 8 to the side walls 4 with screws 5 in threaded openings 6. Bearing surfaces 9 are also screwed into the side walls 4. Tape guides 10 are screwed into the side walls 4. Other stabilizing bars are also screwed into the side walls and extend therebetween under the plate 11. A pair of cutter mechanism retention members 12 are also screwed into the side walls 4. It can be appreciated by those reasonably skilled in the art that the fabrication technique of this nozzle 1 is to secure a multitude of metallic components between a pair of side walls 4. At locations where each of these components meets the side walls 4, there is the potential for leakage of the mastic material. Such leakage is undesirable. This potential for leakage is increased due to the cumulative tolerances of each of the individual components. Although each individual component is precisely machined, the individual components are manufactured within defined tolerance limits. When numerous individual components are secured together, the individual tolerances add together, thereby causing particular components to have a space provided therebetween, magnifying the leakage problem.
An attempt to address the leakage problem includes the application of the silicone sealant to the areas where the mastic tends to escape the nozzle. While the sealant can provide a short term solution to the leakage of material, the sealant can degrade over time and usage. The addition of the sealant also requires additional steps in the assembly and maintenance of the nozzle and adds to the cost thereof.
Because this nozzle is formed of multiple metallic components requiring precision machinery for assembly the cost of manufacturing such a nozzle is high. In addition, field adjustments to the components are required for optimum operation of the nozzle. These adjustments are necessary in order to allow the numerous parts to be tweaked in order to minimize the leakage discussed above. The adjustments also allow the operator to achieve the appropriate dispersion of mastic or mud onto the tape during application. The field adjustment of the components may prove difficult, as the number of components and screws make it difficult to maximize the effectiveness of the tool. It is therefore, very time consuming to adjust the tool in the field. The difficulty of field adjustment is also increased because the operator has to have the appropriate adjustment tools available. Having the appropriate adjusting tools readily available in the field is not always practical.
It would therefore be advantageous to provide a nozzle which minimizes the number of individual components. This would greatly reduce the time required to assemble the nozzle and the cumulative tolerances and field adjustments would be minimized. With the reduction of individual components, the possibility of leakage occurring in the nozzle would also be reduced or eliminated.
This invention addresses the problems with the state-of-the-art nozzles because it provides a substantially unitary design. The unitary nozzle includes a tape receiving opening that extends into a tape path through a fill section to a front end. The unitary design allows for the application of a cutter mechanism, wheels to provide motive force and a mastic tube to supply mastic to the fill section.
This unitary design prevents leakage of mastic material into undesired sections of the nozzle and out of the nozzle. The unitary design also eliminates the need for precision machining and field adjustments because the components are precisely molded or formed into a unitary design during manufacturing. As the nozzle is made from one piece, precision machining of each individual piece to minimize tolerance problems is eliminated and the need for many of the field adjustment members is also eliminated. Service on the nozzle is also reduced in that the application of a sealant is eliminated and adjustments are minimized.